What are the rights of passengers during traffic stops?

Traffic stops typically occur as a result of suspected moving violations committed by the driver of the vehicle. Passengers cannot be held responsible for the driver's conduct and are generally free to leave, unless police become suspicious of them during the course of the stop.

Unfortunately, this happens frequently and the amount of evidence required to detain passengers is minimal. For this reason, passengers must remember to refuse search requests and refrain from answering questions without an attorney present. Police who suspect criminal activity will often separate the occupants of an automobile and question them separately. If their stories differ, this could lead officers to claim that they have probable cause to prolong the detention or conduct a search.

As with any other brief detention, the best way to handle this situation is to ask if you're free to go.

Read this article summarizing a 2007 U.S. Supreme Court decision, Brendlin v. California, protecting the 4th Amendment rights of automobile passengers.